Subject: [linux-audio-dev] LADSPA_HINT_LOGARITHMIC
From: Marcus Andersson (054185595_AT_telia.com)
Date: Tue Sep 04 2001 - 19:16:20 EEST
Hi,
I would like to know if there is any agreed upon logarithmic function to
use for LADSPA control ports when the LADSPA_HINT_LOGARITHMIC is set. In
practice, the function should map display coordinates (the slider) to
control values.
The best I have come up with myself is this:
Control port value, v
Control port low limit, v_low
Control port high limit, v_high
Display coordinates, d
Display coordinates low limit, d_low
Display coordinates high limit, d_high
Transposition to positive range, log_offset
Setup:
log_offset = -v_low+1;
d_low = log(v_low + log_offset);
d_high = log(v_high + log_offset);
d = log(v + log_offset);
Slider moved:
v = exp(d) - log_offset;
Marcus
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